Conventionally, audio signal transmission/reception devices equipped with microphones, speakers, and operation controls have been known, wherein Voicepoint IP shown in Non-Patent Document 1 provided by Nippon Electronic Co. Ltd. (NEC) has been known, for example. FIG. 7 is a perspective view of a conventionally known audio signal transmission/reception device 100. The audio signal transmission/reception device 100 includes a main unit (housing) 101 having a prescribed shape, a speaker 102 mounted on the center of the surface of the main unit 101, a plurality of microphones 103 arranged in the periphery of the speaker 102, and an operation control (console) 104 arranged in the front side of the surface of the main unit 101.    Non-Patent Document 1: Voicepoint IP, NEC (which can be retrieved via the Internet; URL: http://www.nec-eng.com/pro/vp_ip)
The aforementioned audio signal transmission/reception device 100 is applied to an audio signal transmission/reception system including multiple audio signal transmission/reception devices, wherein audio signals converted by the microphones 103 of the audio signal transmission/reception device 100 are transmitted to a counterpart audio signal transmission/reception device and wherein the speaker 102 produces sound based on received audio signals, which are transmitted from the counterpart audio signal transmission/reception device and are received. By arranging the speaker 102 on the surface of the main unit 101, it is possible to arrange the main unit 101 on a desk, thus placing a user's head above the main unit 101.
It allows the user to operate the operation control 104 so as to perform sound reception setups of the microphones 103 and sound emission setups (volumes etc.) of the speaker 102, wherein sound reception setups and sound emission setups can be appropriately changed. The audio signal transmission/reception device 100 is normally arranged on a desk. Hence, the operation control 104 is arranged in the front side of the surface.
The conventionally-known audio signal transmission/reception device 100 is designed so that the speaker 102, the microphones 103, and the operation control 104 are all arranged on the surface of the main unit 101 in consideration of the user operability and sound emission characteristics. For this reason, it is difficult to reduce the size of the main unit 101.
In order to realize hands-free audio signal transmission/reception devices (e.g., telephone devices), it is a recent trend to use speaker arrays having sound emission characteristics of narrow directivities and microphone arrays having sound reception characteristics of narrow directivities. Speaker arrays are each designed to align multiple speakers in order to realize adequate sound emission directivity controls, while microphone arrays are each designed to align multiple microphones in order to realize adequate sound reception directivity controls. For this reason, when a speaker array or a microphone array is applied to the conventionally-known audio signal transmission/reception device 100, the size undesirably increases.